Various vane-type fluid displacement apparatuses have been proposed for use in certain limited applications. These proposed devices have primarily consisted of pumps, compressors, fluid driven motors, and fluid flow meters. The vane-type apparatuses heretofore proposed have generally performed satisfactorily and have gained acceptance for specific liquid applications. Common difficulties encountered with prior art vane-type apparatuses have included: an unsuitability for use with friction-reducing devices, which has traditionally limited their use to moderate power levels; a large fixed-surface to moving-surface contact area, resulting in high friction; an inability to withstand bending forces applied to the crankshaft; a reliance on discrete check valves or the like; and an inability to accommodate simultaneous reciprocating flow from each individual chamber.
Conventionally, a vane or gate compressor typically includes a cam ring, a rotor rotatably received within the cam ring, a drive shaft on which is secured the rotor, a front side block fixed to a front-side end face of the cam ring, a rear side block fixed to a rear-side end face of the same, a front head secured to a front-side end face of the front side block, a rear head secured to a rear-side end face of the rear side block, a plurality of axial vane slits formed in an outer peripheral surface of the rotor at circumferentially equal intervals, and a plurality of vanes radially slidably fitted in the axial vane slits, respectively. The drive shaft for rotating the rotor has opposite ends thereof rotatably supported by radial bearings arranged in the front and rear side blocks, respectively. Typically, a discharge chamber is defined by an inner wall surface of the front head, the front-side end face of the front side block, and the front-side end face of the cam ring, into which flows a liquid or gas delivered from compression chambers.
In another example of a prior art rotary compressor, the compressor mechanism can comprise a shaft adapted to be driven by a drive motor and having its upper and lower ends rotatably received by main and auxiliary bearings, respectively. An intermediate portion of the shaft extends through a cylinder that is fixed in position inside the sealed vessel. An eccentric portion is mounted on a portion of the shaft positioned within the cylinder for rotation together therewith. Further, a ring-shaped roller is operatively positioned between an inner wall surface of the cylinder and an outer peripheral surface of the crank and will, while the shaft is rotatably driven, undergo a planetary motion.
In one example, the cylinder will have a radial groove defined therein so as to extend in a direction radially thereof, and a slidable radial vane is accommodated within the radial groove for movement within the radial groove in a direction towards and away from the ring shaped roller. This slidable radial vane is normally biased by a biasing spring in one direction with a radially inward end thereof held in sliding contact with an outer peripheral surface of the ring-shaped roller such that, by dividing the volume of the cylinder into volumetrically variable, suction and compression chambers are defined on leading and trailing sides of the slidable radial vane, with respect to the direction of rotation of the shaft.
In this example, a liquid or gas is sucked into the suction chamber through the intake port and then compressed before it is discharged through a discharge port during the planetary motion of the ring-shaped roller as a result of the eccentric rotation of the crank. In order to facilitate a sliding motion of the ring-shaped roller relative to the inner wall surface of the cylinder and the radial inner end of the slidable radial vane and also a sliding motion of the radial vane within the radial groove, a quantity of lubricating oil is accommodated within the sealed vessel at a bottom portion thereof. In one example, the lubricating oil is sucked up by an oil pump mounted on the lower end of the shaft to oil various sliding elements within the compressor mechanism.
Of the various sliding elements used in such a conventional compressor mechanism, the slidable radial vane creates a detrimental problem when it becomes worn. As is well known to those skilled in the art, the slidable radial vane is frictionally engaged not only with the ring-shaped roller, but also with side surfaces defining the radial groove in the cylinder. Specifically, by the biasing force of the biasing spring and a back pressure acting on the trailing surface of the slidable radial vane, the radial inner end of the slidable radial vane is constantly held in frictional engagement with the ring-shaped roller and, also, opposite side surfaces of the slidable radial vane are alternately held in frictional engagement with the corresponding side surfaces defining the radial groove by the effect of a pressure difference between the suction and compression chambers. Unlike other sliding elements such as, for example, the shaft and its bearing mechanism, the slidable radial vane is not lubricated by the lubricating oil supplied directly by the oil pump, but is typically lubricated by an oil component, contained in the liquid or gas being compressed, and/or an oil leaking from roller ends. The quantity of the oil available from the fluid being compressed and leaking from the roller ends is normally insufficient for lubricating the slidable radial vane and its surrounding parts satisfactorily. In addition, considering that the fluid reaches an elevated temperature when compressed, the slidable radial vane in contact with the fluid being compressed becomes heated and is therefore susceptible to an accelerated frictional wear.
In such conventional vane pumps, as speed of the pump is increased, the centripetal force acting on the vane(s) presses them aggressively against the inner surface of the constraining housing, which beneficially provides a solid sealing force but also detrimentally creates high frictional forces between the vane's distal end and the inner surface of the housing. As one skilled in the art will appreciate, this increases frictional wear as well as reduces the compressor's operating efficiency.
U.S. Pat. No. 3,821,899 teaches a vane-type meter for use with petroleum or other fluid products. Its structure comprises: a housing having an inlet port and an outlet port; a rotating interior disc; an interior shaft held with respect to the rotating disk in a fixed, eccentric position with respect to the rotating disc; four radially extending, articulated vanes which rotate within the housing about the interior shaft; and four valving structures extending perpendicularly from the outer periphery of one side of the rotating disc. Each of the vanes includes an inner vane element consisting of: a substantially flat body; a single closed ring which extends from one end of the body and is rotatably positioned around the interior shaft; and an elongate, open C-shaped groove extending along the opposite end of the body. Each articulated vane also includes an outer vane element consisting of: a substantially flat body; an elongate pentil structure is formed along one end of the body and pivotally held in the C-shaped groove formed on the inner member; and a second elongate pentil structure formed along the other end of the body. The second pentil structure is pivotally held in one of the valving structures.
Fluid flow through the meter of U.S. Pat. No. 3,821,899 causes the disc, valving ports, and articulated vanes to rotate within the meter housing. As they rotate, the vanes form compartments, which change in volume and through which known amounts of liquid, are transferred from the inlet to the outlet of the device. Thus, the rotational speed of the device provides a direct indication of the fluid flow rate.
U.S. Pat. No. 2,139,856 discloses a pump or fluid-driven engine employing articulated vanes having shaped outer surfaces. The vanes form fluid chambers which continuously change in volume. In one embodiment, the apparatus of U.S. Pat. No. 2,139,856 comprises: a housing; a cylindrical casing held in fixed position within the housing; a crankpin mounted in the casing for eccentric revolving movement; eight articulated, two-part vanes, each having an inner end pivotally connected to the crankpin and an outer end pivotally connected to the casing; eight flow ports provided through a sidewall of the displacement chamber; a flow chamber provided between the casing and the housing; and eight flow ports and associated check valves provided in the casing between the outer ends of the vanes.
In a second embodiment of the device of U.S. Pat. No. 2,139,856, the crankpin is held at a fixed eccentric position within the casing and the casing rotates within the housing. As the casing rotates about the eccentrically positioned crankpin, the compartments formed by the articulated vanes successively draw fluid from inlet ports formed through one of the flat sidewalls of the displacement chamber, and then discharge the fluid through one or more fixed ports in the housing. Each of the articulated vanes has either one or two closed rings formed on the inner end thereof. These inner closed rings are rotatably positioned around the crankpin.
As previously noted, devices such as those proposed by U.S. Pat. No. 2,139,856 and U.S. Pat. No. 3,821,899 have several shortcomings. First, the devices fail to provide any adequate means for reducing frictional forces generated within the moving articulated vane assemblies. Additionally, the cost and complexity of the devices is significantly increased by the required use of completely separate fluid intake and discharge valve systems and/or port structures. Further, the devices provide no means for creating, accessing, and utilizing reciprocating flow regimes between adjacent pairs of articulate vanes. Also, the devices disclose no means for selectively configuring the vanes and displacement chambers in order to obtain specific desired flow patterns. Additionally, these designs have large and significant areas of metal-to-metal sliding contact with no means shown for reducing friction between the parts.
Thus, what is needed is a rotary fluid-displacement assembly that experiences reduced frictional forces within its articulated rotary assemblies. Additionally, the fluid-displacement assembly should be one that can be assembled, operated, and maintained cost effectively. Further, the fluid-displacement assembly should be one that is more efficient and produces less noise and vibration during operation.